1. Field of the Invention
The present invention concerns a distribution frame which is intended for interconnecting the terminals of first connectors linked to the ends of first cables to the terminals of second connectors linked to the ends of second cables through link cords.
A distribution frame for a telephone exchange is particularly intended for connecting first telephone line cables referred to as external cables to second cables referred, to as internal cables, serving the switching equipments in the telephone exchange. The external cables are linked to the first connectors, referred to as cable heads, which are possibly provided with overcurrent or overvoltage protective means. The internal cables are linked to the second connectors, referred to as connection strips. The link cords, called "jumpers" or "flexible conducting cords," enable internal variable connections to the distribution frame to be made between the external and internal cables via the cable heads and the connection strips.
2. Description of the Prior Art
The known description frames may be split into two main types. One is described as a double-sided frame, and the other is described as a tunnel distribution frame.
Double-sided distribution frames are described in French Patent Application No. 2,229,177 and French Patent Application No. 2,317,843 claiming the priority of U.S. Patent Application Ser. No. 591,037 filed June 27, 1975 now U.S. Pat No. 4,002,856. They are composed of horizontal rows of cable heads which include over-current and over-voltage protective means and to which the network multipair cables are connected, and horizontal rows of connection strips to which the multipair cables coming from the switching equipments are connected. Each cable head is arranged vertically and each connection strip is laid horizontally. The heads and strips are mounted on a parallelepiped metallic structure having two main vertical sides carrying the rows of strips and the rows of heads respectively. Between these two sides, a trellis work of bars and vertical and horizontal cross pieces carries the link cords, each of which links one terminal pair of a cable head on one of the sides to one terminal pair of a connector strip on the other side.
The separation of the cable head positions and the connection strip positions in a double-sided distribution frame enables work teams belonging to different departments, dealing with lines and switching for instance, to carry out the many wiring operations. However, as a result of this separation, the types of cable heads and connection strips used do not always match and the latter are not arranged for the link cords to be of an optimum length.
Such an arrangement implies, for most of the links to be created, that two factors be brought into play to connect a link cord. Indeed, the length of the link cord is variable and sometimes very long. Moreover, due to the lack of coordination between the departments assigned to the external lines and those assigned to the internal installation at the exchange, the cable heads and connection strips are not arranged with the same thought as regards optimizing link cord disposition. The routing rule for a link cord which should be respected, namely horizontal routing along the horizontal connection strip and a change of level in line with the corresponding cable head, is followed unfortunately only to a very small extent. What is more, since accessibility to the first link cords laid in place is in certain cases rather difficult, they cannot be removed. The accessible routes thus become congested and it is impossible to make many of the links.
A second type of distribution frame, referred to as the tunnel type, is disclosed in French Patent Application 2,340,658. This type adopts an inverted U structure having inner vertical and parallel lateral sides for carrying the connection strips and the cable heads respectively. The horizontal upper part of the frame joins the two lateral sides and carries cradle stirrups having fingers through which the link cords pass. The link cords rise vertically upwards from the connection strips along the corresponding inner side, then run horizontally across the upper tunnel part and finally drop down vertically to the cable heads along the other inner side.
Amongst the drawbacks of the tunnel distribution frame, the following can be mentioned. The link cords are necessarily very long since all of them must run via the upper part of the frame. There are therefore no short link cords. In addition, the frame must not be too high so as not to hinder the positioning of the link cords. As a result, use of a tunnel frame is restricted to a dependent telephone exchange which serves a relatively low number of telephone lines.
Furthermore, the German Patent Application No. 2,315,485 teaches a distribution frame for a telephone exchange. In this frame, first connectors also called distributors serve first cables and are arranged as per a first upper vertical sub-matrix and second connectors serve second cables and are arranged in a lower vertical sub-matrix positioned below the first sub-matrix. The two sub-matrices are co-planar and the columns or rows of connectors in the two sub-matrices are colinear two-by-two.
In this distribution frame, the two sub-matrices thus form two wholly individual assemblies, respectively upper and lower. Horizontal and vertical guides are provided between these two assemblies, such as stirrups or horizontal section rings through which the link cords are fed. Each cord links a first connector in any one column of the first sub-matrix to a second connector in any one column of the second sub-matrix.
The latter frame type is therefore analogous to a tunnel frame having a U section with lateral sides that have been flattened out into a vertical plane. Consequently, the drawbacks of this frame are analogous to those already broached for a tunnel distribution frame. Indeed, the jumpers or connection cords need to be very long since all of them must run through the stirrup guides between the two sub-matrices. As a result, there are no short link cords. In addition to this, the frame height must be small, and be decidedly less than that of the tunnel frames, since it is about three times that of a sub-matrix. This type of frame is therefore geared to use in a dependent telephone exchange which serves a relatively small number of telephone lines.